Etching process.



E. ALBERT.

ETGHING PROCESS.

APPLIGATION FILED MAY 25, 1912.

1,081,990,. Patented; Dec. 16, 1913.

EUGEN ALBERT, 0F MUNICH, GERMANY.

ETGHING PROCESS.

Specification of Letters Patent.

Patented Dec 16, 1913.

Application filed May 25, 1912. Serial No. 699,690.

This invention relates to the process of etching metal plates forprinting purposes and the like by means of acid in a bath, and has forits object to render the process more effective and more expeditious.

The etching process in most etching machines is achieved by violentlyagitating the acid on the surface of the object. being etched in orderto renew the particular molecules in action as frequently as possible ina given unit of time; the mechanical force of the movement also removesthe oxid from the etched surface which would otherwise prevent theetching action.

Most of the constructions hitherto employed in carrying out the etchingprocess, suffer from the disadvantage that steel and iron, or similarmaterials, can not be employed, even where considerable mechanicalstrains occur, owing to the action of the acid.

New conditions obtain in the application of the present process, acurrent of air being conducted against the plate or other objectsituated in the acid and a resistance being interposed either directlyor indirectly in the path of the air current. Vlfhen a direct resistanceis interposed a violent whirling or ebullient movement of the acidoccurs,

but, if, say, a single air current is projected from a slit nozzle on tothe liquid, an air furrow is produced and the resistance is an indirectone due to the deformation of the level surface of the liquid and theliquid trying to regain its original form. In this latter case theeffect is attained that the particles of liquid move quickly over thesurface of the plate under considerable pressure. The dimensions of thefurrow, or air groove, produced depend on the velocity with which thecompressed air issues from the outlet opening. The etching action variesconsiderably within the active zone of this air furrow. ltf we supposethat this air furrow is about two inches deep then it will be clear thatthe etching action on any object situated much deeper than two incheswill not be very efi'ective. Gin the other hand if the article to beetched be raised too high, the air current will drive all the acid awayfrom some areas of the object leaving the surface quit dry. Betweenthese positions, there is what may be termed the active zone into whichthe article to be etched is brought, so that the violently agitated acidshall be able to remove the oxid formed. It is evident that in orderuniformly to etch large areas, the article to be etched and the airoutlet should be moved relatively to each other. if a direct resistancebe opposed to the movement of the acid induced by the current of airapplied as stated, the etching acid is broken up and the kinetic energyimparted to the particles of liquid is expended in the production ofwhirling movements. The agitating move ment of the acid acquired in thiswhirling zone-that is the space between the air outlets and theresistance-can be restricted, while the acid situated outside of thiszone is at rest on the upper surface. The intensity of the liquidagitation in the whirling zone depends on several factors. The airoutlet may be varied; it may consist of a rose, or sprinkler, providedwith a number of holes, but to avoid frictional losses, it mayadvantageously consist of slotted open ings. Furthermore the intensityof the liquid movement on the surface of the object to be etched dependsas before on the relative position of the parts; if, for cX- ample, theobject is situated some six or seven inches below the surface of theacid, then the whole weight of liquid situated above the objectwould beopposed to the production of the whirling movement, and would diminishits effect; also considerable power is wasted if the distance betweenthe air outlet and the object to be etched is too great; in both cases,a corrcspoiuliug increase in the pressure of the compressed air isrequired in order to overcome the resistance. it will be seen thereforethat either with or without a direct resistance opposed to the aircurrent, it is advisable to arrange the object to be etched near thesurface of the acid.

The accompanying drawing shows a practical means of applying my processin which a direct resistance is opposed to the air current, the saidresistance being formed firstly,,by a second air current, both aircurrents being of lineal form and converging toward the object to beetched, and secondly, by the object itself.

Figure 1 shows an arrangement in which the resistance is formed by anair current; and Fig. 2 is a modification in which the resistance isformed by the object to be etched, in this instance, a roller.

Referring to Fig. 1, a is a trough or tray which is filled up to 6 withacid; 0 is the flexible tube for supplying compressed air, 5 is thenozzle which conducts the air in two converging currents against theobject d to be etched, situated beneath the surface of the acid. f isthe whirling or agitated zone and g the exhaust tube through which theinjurious acid vapors can exhaust into the open without the use of anyfan, or the like, but merely owing to the pressure of the air blastwithin the saddle-shaped double nozzle 6. Now in order that the etchingprocess may be carried out uniformly, the air current and the object tobe etched must move relatively to each other, which is most easilyobtained by slowly and uniformly moving the trough. In this arrangementthe whole movement of the acid takes place in the body of the blastnozzle and consequently the trough can be quite open and does not needany protecting device for preventing the splashing out of any acid. Itis thus easily interchangeable for various acids and the acid vapors canbe exhausted without any expense through an exhaust tube by the currentof air. According to thisinvention therefore, new constructiveconditions are brought into play; only the trough and the air outletdevices need be acid-proof, and none of the parts are eX- posed to anymechanical strain. Besides this example, many other arrangements arepossible; any number of air outlets of any desired shape may be providedand thus such a uniform distribution of the power of the air current,and whirling factor, be obtained that only a small equalizing movementof the article to be etched, or of the blast, will be necessary, indeedin some cases no movement ofeither will be required.

In certain cases the object to be etched may constitute the resistance,as when etching a round body, for example a roller, or the like. Thismodification is shown in cross section in Fig. 2, in which the roller ddips below the surface of the acid 0 in the trough a, and air brought bythe tube 0 is blown from the side through the blast nozzle 1), c as faras possible along the whole breadth of the roller to be etched, so thatthe acid thus brought into movement strikes against the roller d whichforms a resistance. With intermittent action of .the air current anincreased resistance may be formed by the liquid itself.

What I claim as my invention and desire v to secure by Letters Patentis 1. The process of etching consisting in directing a current ofcompressed air on to the etching acid, producing a resistance to thesaid air current by the deformation of the liquid surface into a furrow,or air groove, placing a part of the object to be etched just beyond thesurface of the acid in said furrow, and displacing the etched portion ofsaid object and the air current in relation to each other, substantiallyas and for the purpose set forth.

2. The process of etching consisting in directing a current of airagainst the object to be etched placed just beneath the surface of theetching acid, and in opposing a resistance to the movement of the liquiddisplaced by the air current so that the liquid is broken up andagitated, substantially as described herein.

3. The process of etching consisting in directing a current of airagainst the object to be etched placed just beneath the surface of theetching acid, and in opposing a direct resistance to the movement of theliquid displaced by the air current by means of a second air current,substantially as and for the purpose set forth.

4. The process} of etching consisting in directing a current of airagainst the object to be etched placed just beneath the surface of theetching acid, and in opposing a direct resistance to the movement of theliquid displaced by the air current by means of a second air current thetwo said air currents converging toward the surface of the object to beetched, substantially as described herein.

5. The process of etching consisting in directing a current of airagainst the object to be etched placed just beneath the surface of theetching acid, and in opposing a direct resistance to the movement of theliquid displaced by the air current by means of a second air current thetwo said air currents converging toward the surface.

of the object to be etched and being of a concentrated lineal characterapplied transversely of the object, and in producing relative to eachother a movement between said object and the air blast, whichmovementhas a longitudinal direction as re- Tia UGEN ALBERT. V

Witnesses l A. V. W. COTTER, MA'IHILDE K. HELD.

